simplified code across the app and consolidated duplicated helpers

lib/push/push_actions.dart

@@ -1,5 +1,4 @@
 import 'dart:async';
-import 'dart:convert';
 import 'dart:developer';
 import 'dart:ui';
 
@@ -13,6 +12,7 @@ import '../session/session_manager.dart';
 import 'chat_thread_store.dart';
 import 'nid_store.dart';
 import 'push_renderer.dart';
+import 'push_target.dart';
 
 /// Notification action identifiers shared between the renderer (which attaches
 /// the actions) and the response handlers (which dispatch them).
@@ -93,8 +93,7 @@ class PushActions {
           // the mark-read action does. Best effort: a failure here must not
           // fail the already-delivered reply.
           await markRead(chatToken);
-        }
-        if (!result.ok) {
+        } else {
           // Never swallow the typed message: surface the failure (and the
           // undelivered text) as its own notification. The nid mapping stays
           // alive — the thread notification is still in the tray.
@@ -287,14 +286,6 @@ class PushActions {
     return raw == null ? null : int.tryParse(raw);
   }
 
-  static String? _payloadField(String? payload, String key) {
-    if (payload == null || payload.isEmpty) return null;
-    try {
-      final map = jsonDecode(payload) as Map<String, dynamic>;
-      final value = map[key];
-      return value?.toString();
-    } on Object {
-      return null;
-    }
-  }
+  static String? _payloadField(String? payload, String key) =>
+      decodeNotificationPayload(payload)?[key]?.toString();
 }